Silica glass member for hermetic sealing of ultraviolet smd led element and method for manufacturing quartz glass member for ultraviolet led

ABSTRACT

Provided is a silica glass member for hermetic sealing of an ultraviolet SMD LED element to be suitably used for hermetic sealing of, and as a transmission window material for, a surface mount-type package (SMD) having an ultraviolet LED mounted thereon and configured to emit ultraviolet light in a wavelength range of from 200 nm to 350 nm. The silica glass member for hermetic sealing includes a silica glass substrate, which is homogeneously and integrally formed without an internal boundary, wherein the silica glass substrate has: a first surface on an inside opposed to an SMD LED element; and a second surface on an outside corresponding to the first surface, wherein an outer peripheral portion of the first surface has formed therein a substrate joining plain surface for joining to the container outer periphery joining plain surface, and wherein the second surface on the outside corresponding to the first surface has formed therein a lens-like convex portion configured to process emitted light from the ultraviolet SMD LED element.

TECHNICAL FIELD

The present invention firstly relates to a silica glass member to beused for hermetic sealing of an ultraviolet LED configured to emitultraviolet light in a wavelength range of from 200 nm to 350 nm, andmore specifically, to a silica glass member to be suitably used forhermetic sealing of, and as a transmission window material for, asurface mount-type package (commonly called a surface mount device(SMD)) having an ultraviolet LED mounted thereon and configured to emitultraviolet light in a wavelength range of from 200 nm to 350 nm. Thepresent invention secondly relates to a method of manufacturing a quartzglass member for an ultraviolet LED at a wavelength of from 200 nm to400 nm.

BACKGROUND ART

An ultraviolet LED configured to emit light in a deep ultravioletwavelength band is expected to be applied in a wide range of fields,such as virus sterilization, drinking water, air purification, resincuring, decomposition of environmental pollutants, a food field, andvarious kinds of medical equipment.

A gas light source, such as a mercury lamp, has been used as an existingdeep ultraviolet light source. However, a range of use of the gas lightsource is limited because of its short lifetime, its emissionwavelength, which is limited only to an emission line of a gas, asubstance contained therein that is harmful to a human body/environment,such as mercury, and an extremely large size and power consumption ofthe light source. Therefore, there has been an increasing demand forrealization of an alternative technology. Under such circumstances, itis strongly desired to develop a mercury-free, low-environmental-load,downsized, high-output ultraviolet LED, and an ultraviolet LED using anitride-based semiconductor (AlGaN) has been actively developed.

The ultraviolet LED emits light having a wavelength of from 200 nm to400 nm, and has a problem in that a lens made of a silicone resin, whichhas hitherto been used for a visible light LED, undergoes deteriorationof the resin or does not transmit the light.

In addition, there is also a problem in that light extraction efficiencyfrom an ultraviolet LED element is extremely low. Accordingly, amaterial that absorbs as little light as possible is required also for awindow material or a lens material, and use of an optical member made ofquartz glass has been considered (Patent Documents 1 and 2).

However, there are problems in that, with a window plate made of quartzglass, light is diffused, and hence a desired light intensity is notobtained, and a hemispherical lens is difficult to mount on a package.

Meanwhile, an injection molding method is known as a method ofmanufacturing a quartz glass member with high accuracy in dimensions andshape (Patent Documents 9 and 11).

This method can provide a transparent quartz glass body by degreasingand purifying a molded body, followed by firing, but has a problem inthat purification treatment with chlorine or hydrogen chloride generatesan optical absorption band at a wavelength of about 250 nm (5.0 eV) dueto an oxygen-deficient defect (Non Patent Document 1).

In addition, there is a proposal of a method involving, aftervitrification, repairing the oxygen-deficient defect with an atmospherecontaining oxygen or an atmosphere containing water vapor. However, themethod is limited in its effect to a quartz glass surface and requirestreatment at high temperature. Accordingly, there is a risk of areduction in transmittance due to an influence of contamination with animpurity (Patent Documents 18 and 19).

In addition, in recent years, rapid progress has been made in shorteningwavelengths of semiconductor light-emitting elements (LEDs). Of those,an ultraviolet LED having, as its emission region, ultraviolet lighthaving a relatively long wavelength (commonly called UVA, and fallingwithin a wavelength range of from 380 nm to 315 nm) has already been putinto practical use for curing a UV-curable resin.

UVB (falling within a wavelength range of from 315 nm to 280 nm) and UVC(falling within a wavelength range of from 280 nm to 200 nm) each havinga shorter wavelength than UVA are currently being intensively developed.In particular, UV light having a wavelength of around 260 nm, which iscalled a germicidal ray, has an intense germicidal action, and hencethere is a demand that its practical use be soon achieved as inexpensivemeans for sterilizing water or sterilizing air.

It is said that there are significant technical obstacles between UVAand UVB or UVC. One of the obstacles is a substrate material, andanother is a transmitting material. UVA is formed on a sapphiresubstrate (Al₂O₃), but UVB and UVC each require an AlN substrate due tolattice constant matching.

Meanwhile, for ultraviolet light of UVA, a window or a lens can beformed using an organic resin having a high UV transmission property,such as a silicone or Teflon (trademark). However, for ultraviolet lightof UVB or UVC, such organic material is insufficient in terms of lighttransmission property, and is also insufficient in terms of durabilityagainst UV light. In addition, a borosilicate-based glass materialhaving a satisfactory UV transmission property, which is often used forUVA, LED, also cannot be used due to problems with the lighttransmission property (even borosilicate glass hardly transmitsultraviolet light having a wavelength of 350 nm or less) and thedurability.

For this reason, silica glass has been exclusively used as a windowmaterial or lens material for a UVB-LED or a UVC-LED (Patent Documents 1and 2). The silica glass has a high transmission property for UV lightand also has high durability, and hence has sufficient characteristicsas the window material or lens material for a UVB-LED or a UVC-LED.However, the silica glass needs polishing in order to constitute asmooth surface having a high light transmission property suitable as thewindow material or the lens material, and hence cannot integrallyconstitute a smooth surface in a member in which a plain surface and aspherical surface coexist. For example, when, as proposed in the presentinvention, an outer peripheral portion has a plain surface and astructure having a convex spherical surface shape is formed inside acentral side, a planar silica glass plate material and a hemisphericallens need to be each independently produced, polished, and bonded toeach other.

However, from the viewpoint of serving as a member for a UVB-LED or aUVC-LED, there is hardly any adhesive having a sufficient transmissionproperty and sufficient durability in such wavelength region.

In addition, mounting of LEDs, not limited to ultraviolet LEDs, isclassified into a shell-type package and an SMD-type package. An LEDelement is an extremely fragile semiconductor element, and hence needsto be kept in a sealed environment for the purpose of preventingdeterioration due to moisture or the like in the atmosphere. Theshell-type package is a package in which a surrounding space of an LEDis sealed with a resin, and is widely used as an inexpensive LEDpackage.

Meanwhile, the SMD package has a structure in which an LED element ismounted on a concave recessed portion, a bottom surface and a side wallsurface are each constituted of a reflector, and an upper surface istightly sealed with a window material for hermetic sealing (PatentDocument 3).

Further, when output is insufficient with one LED element, a multi-typepackage in which a plurality of elements are arranged in one package isalso beginning to be widely used.

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: JP 2015-133505 A-   Patent Document 2: JP 2015-179734 A-   Patent Document 3: JP 2009-99759 A-   Patent Document 4: WO 2006-85591 A1-   Patent Document 5: JP 2006-232582 A-   Patent Document 6: JP 2006-248798 A-   Patent Document 7: JP 2006-290666 A-   Patent Document 8: JP 2006-315910 A-   Patent Document 9: JP 2006-321691 A-   Patent Document 10: JP 2014-15389 A-   Patent Document 11: JP 4446448 B2-   Patent Document 12: JP 4484748 B2-   Patent Document 13: JP 4498173 B2-   Patent Document 14: JP 4539850 B2-   Patent Document 15: JP 5177944 B2-   Patent Document 16: JP 5512084 B2-   Patent Document 17: JP 5830502 B2-   Patent Document 18: JP 2008-195590 A-   Patent Document 19: JP 2009-203144 A

Non Patent Document

-   Non Patent Document 1: H. Imai et al. (1988) Two types of    oxygen-deficient centers in synthetic silica glass. Physical    Review B. Vol. 38, No. 17, pp. 12772-12775

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

A first object of the present invention is to provide a silica glassmember to be used for hermetic sealing of an ultraviolet LED configuredto emit ultraviolet light in a wavelength range of from 200 nm or moreto 350 nm or less, in particular, a silica glass member for hermeticsealing of an ultraviolet surface mount device (SMD) LED element to besuitably used for hermetic sealing of, and as a transmission windowmaterial for, a surface mount-type package (commonly called an SMD)having an ultraviolet LED mounted thereon and configured to emitultraviolet light in a wavelength range of from 200 nm or more to 350 nmor less. A second object of the present invention is to provide a methodof manufacturing a quartz glass member for an ultraviolet LED, whichinvolves repairing an oxygen-deficient defect so that there can beobtained a quartz glass member for an ultraviolet LED improved in lightabsorption at a wavelength of about 250 nm and free of absorption due toa structural defect at a wavelength of from 200 nm to 400 nm.

Means for Solving Problems

According to one embodiment of the present invention, there is provideda silica glass member for hermetic sealing of an ultraviolet SMD LEDelement that is configured to emit light in a wavelength range of from250 nm to 350 nm and is placed in a hermetic sealing container having acontainer outer periphery joining plain surface formed in an outerperipheral portion thereof, the silica glass member for hermetic sealingincluding a silica glass substrate, which is homogeneously andintegrally formed without an internal boundary, wherein the silica glasssubstrate has: a first surface on an inside opposed to the SMD LEDelement; and a second surface on an outside corresponding to the firstsurface, wherein an outer peripheral portion of the first surface hasformed therein a substrate joining plain surface for joining to thecontainer outer periphery joining plain surface, and wherein the secondsurface on the outside corresponding to the first surface has formedtherein a lens-like convex portion configured to process emitted lightfrom the ultraviolet SMD LED element.

A plurality of the lens-like convex portions are suitably formed on thesecond surface. The substrate joining plain surface formed in the firstsurface preferably has a surface accuracy of 1 μm or less and a surfaceroughness of 0.1 μm or less in terms of Ra value, and the lens-likeconvex portion in the second surface preferably has a surface roughnessof 0.2 μm or less in terms of Ra value.

The silica glass member for hermetic sealing of the present inventionsuitably has an internal transmittance at a thickness of 3 mm of 95% to99% for ultraviolet light having a wavelength of 300 nm to 400 nm and aninternal transmittance at a thickness of 3 mm of 92% to 99% or less forultraviolet light having a wavelength of 245 nm or more and less than300 nm.

In the silica glass member for hermetic sealing of the presentinvention, bubbles contained in the silica glass member for hermeticsealing each preferably have a diameter of 50 μm or less, and thebubbles contained preferably have a total cross-sectional area of 1×10⁻³mm² or less per 0.1 cm³ of a volume of the silica glass member forhermetic sealing.

In the silica glass member for hermetic sealing of the presentinvention, respective differences between internal transmittances of thesilica glass member for hermetic sealing at a thickness of 3 mm forultraviolet light having wavelengths of 350 nm, 300 nm, and 250 nmmeasured using an integrating sphere and internal transmittances thereofat a thickness of 3 mm for ultraviolet light having wavelengths of 350nm, 300 nm, and 250 nm in general measurement are each suitably within0.5%.

The silica glass member for hermetic sealing of the present inventionpreferably contains OH groups at a concentration of 0.1 ppm to 20 ppm.

The transmittance measurement with the integrating sphere is described.In the transmittance measurement of silica glass in which internalscattering due to a bubble or a granular structure exists, atransmittance measurement apparatus based on a general optical systemcannot distinguish between internal absorption and a scattering loss,and hence allows the scattering loss to be measured as absorption.Meanwhile, a transmittance measurement apparatus including theintegrating sphere, which is applicable to UV light, enables alsoscattered light to be introduced into a photodetector, and hence enablesan absorption amount excluding the scattering loss to be measured. Inother words, an internal transmittance obtained by the transmittancemeasurement using the integrating sphere is considered not to includethe scattering loss, and hence enables the scattering loss to beestimated through a comparison to an internal transmittance obtained bythe general transmittance measurement. Specifically, the followingequation holds: internal transmittance obtained by general transmittancemeasurement (=internal absorption+scattering loss)−internaltransmittance obtained by integrating sphere measurement (internalabsorption)=scattering loss. In actuality, even the integrating spheremeasurement cannot pick up all the scattering loss, and hence it isreasonable to consider that part of the scattering loss is measured.However, the intensity of the scattering loss can be specified throughthis comparison.

The silica glass member for hermetic sealing of the present invention issilica glass suitable for a transparent window material and/or a lensmaterial for an LED configured to emit ultraviolet light of UVB or UVC,in which the window material and the lens material, which haveoriginally been separately cut out and subjected to polishingprocessing, are integrally formed, thereby having an advantage of beingable to be inexpensively supplied. In addition, in this case, when aplurality of lens portions are simultaneously formed in one silica glassmember for sealing, there is an advantage in that a further cost effectis obtained.

As specific means, powder of synthetic silica glass is mixed and kneadedwith a binder, and the mixture is subjected to press molding in a moldfor molding a required shape to provide a green body, which is subjectedto heat treatment to be made transparent. Thus, a silica glass moldedbody for hermetic sealing of the present invention having a complicatedshape integrally and homogeneously formed into a predetermined shape canbe obtained.

Originally, some requirements need to be satisfied in order toconstitute a window material or a lens material for ultraviolet lighthaving a short wavelength, such as UVB or UVC, by mold molding usingsilica glass powder as a starting material. That is, the following arerequired in order to obtain the required transmittance, lightdurability, and moldability: the purity and particle size of the silicaglass powder serving as the starting material be appropriatelycontrolled; the inner surface finish of the molding mold be sufficientlysmooth so as not to require post-polishing; structural defects of silicaglass generated in the degreasing and molding steps be sufficientlysuppressed/cured; and gaps between particles of the powder or adissolved gas be sufficiently removed, to thereby reduce bubbles toprevent unnecessary scattered light from being emitted.

The integral molding of the silica member by the mold molding has agreat advantage in terms of manufacturing method in that a plurality oflens portions can be simultaneously formed. Particularly among LEDpackages in recent years, there have been an increasing number ofpackages each having placed therein a plurality of LEDs for the purposeof increasing the output. In this case, it is important that thepositional relationship between individual LEDs and lens portions beaccurately adjusted.

In the present invention, a window material and lens-like convexportions are manufactured in a state of being integrally formed, and asa result, the position of each of the lens portions is determined as atransfer of a position designed as a mold. Accordingly, there is anadvantage in that the position can be extremely accurately determined.As the mold molding of a silica member, besides the press molding, thereare known injection molding, transfer molding, a slip casting method,and the like (Patent Documents 4 to 17).

According to another embodiment of the present invention, there isprovided a method of manufacturing a quartz glass member for anultraviolet LED, including: a molding step of mixing silica powder and abinder component, followed by molding the resultant mixture to obtain amolded body having a predetermined shape; a heat treatment step ofsubjecting the molded body to heating treatment with various gases; anda vitrification step of vitrifying the molded body subjected to heattreatment into transparent glass after the heat treatment step, whereinthe heat treatment step includes: a degreasing step for organic matterat 1,000° C. or less with an atmosphere containing oxygen; apurification step for a metal impurity at 1,200° C. or less with anatmosphere containing hydrogen chloride after the degreasing step; and astep of promoting repairing of an oxygen-deficient defect at awavelength of about 250 nm at 1,150° C. or less with an oxidizingatmosphere after the purification step.

The molding step suitably includes a molding step with a metal mold.

The oxidizing atmosphere suitably includes an atmosphere containingoxygen and/or water vapor.

The vitrification step is suitably performed at 1,700° C. or less.

The silica powder suitably contains at least one kind of sphericalsilica, and the silica powder suitably has an Al concentration of 70 ppmor less.

The method of manufacturing a quartz glass member for an ultraviolet LEDsuitably further includes performing heating treatment with a hydrogenatmosphere after the vitrification step.

The ultraviolet LED is suitably configured to emit ultraviolet lighthaving a wavelength of from 200 nm to 400 nm.

Advantageous Effects of the Invention

First, the present invention exhibits the remarkable effect capable ofproviding the silica glass member to be used for hermetic sealing of anultraviolet LED configured to emit ultraviolet light in a wavelengthrange of from 200 nm to 350 nm, in particular, the silica glass memberfor hermetic sealing of an ultraviolet SMD LED element to be suitablyused for hermetic sealing of, and as a transmission window material for,a surface mount-type package (SMD) having an ultraviolet LED mountedthereon and configured to emit ultraviolet light in a wavelength rangeof from 200 nm or more to 350 nm or less.

Secondly, the present invention exhibits the remarkable effect capableof providing the method of manufacturing a quartz glass member for anultraviolet LED, which involves repairing an oxygen-deficient defect sothat there can be obtained a quartz glass member for an ultraviolet LEDimproved in light absorption at a wavelength of about 250 nm and free ofabsorption due to a structural defect at a wavelength of from 200 nm to400 nm.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional explanatory view for illustrating a case oneembodiment in which an ultraviolet SMD LED element is sealed with oneembodiment of a silica glass member for hermetic sealing according tothe present invention.

FIG. 2 is a planar explanatory view of the silica glass member forhermetic sealing illustrated in FIG. 1.

FIG. 3 is a schematic perspective explanatory view of the silica glassmember for hermetic sealing illustrated in FIG. 1.

FIG. 4 is a cross-sectional explanatory view for illustrating anotherembodiment of a silica glass member for hermetic sealing according tothe present invention.

FIG. 5 is a cross-sectional explanatory view for illustrating stillanother embodiment of a silica glass member for hermetic sealingaccording to the present invention.

FIG. 6 is a graph for showing the measurement results of thetransmittance of a silica glass member produced in Example 1 togetherwith the theoretical transmittance of silica glass.

FIG. 7 is a graph for showing the measurement results of thetransmittance of the silica glass member produced in Example 1 obtainedusing an integrating sphere together with measurement results obtainedby general measurement.

FIG. 8 is a graph for showing the measurement results of thetransmittances of silica glass members produced using adhesives A to Ein Comparative Example 1 together with the transmittance of the silicaglass member of Example 1.

FIG. 9 is a graph for showing the transmittance measurement results of aquartz glass member for an ultraviolet LED obtained in Example 2 atwavelengths of from 200 nm to 400 nm.

FIG. 10 is a graph for showing transmittance measurement results of aquartz glass member obtained in Comparative Example 2 at wavelengths offrom 200 nm to 400 nm.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention are described below with referenceto the attached drawings. However, these embodiments are described asexamples, and it is understood that various modifications may be madethereto without departing from the technical spirit of the presentinvention.

One embodiment of a silica glass member for hermetic sealing accordingto the present invention is described below. FIG. 1 to FIG. 3 areexplanatory diagrams for illustrating a case in which ultraviolet SMDLED elements 12 are sealed with one embodiment of a silica glass member10 for hermetic sealing according to the present invention. FIG. 1 is across-sectional explanatory diagram, FIG. 2 is a planar explanatorydiagram, and FIG. 3 is a schematic perspective explanatory diagram. InFIG. 1, reference numeral 14 denotes a hermetic sealing container, whichhas a bottom wall 16 and a side wall 18, and is configured to openupward through an opening 20. The upper surface of an upper end outerperipheral portion 22 of the side wall 18 of the hermetic sealingcontainer 14 is formed to be a plain surface to serve as a containerouter periphery joining plain surface 22 a. The ultraviolet SMD LEDelements 12 are placed on the upper surface of the bottom wall 16. Inthe example illustrated in FIG. 1 and FIG. 2, there is illustrated anexample in which two ultraviolet SMD LED elements 12 are placed.However, two or more ultraviolet SMD LED elements 12 may be arranged,and for example, four or six ultraviolet SMD LED elements 12 may bearranged.

The silica glass member 10 for hermetic sealing of the present inventionis not particularly limited in terms of dimensions as long as theopening 20 of the hermetic sealing container 14 can be sealed therewith.For example, in the case of the example illustrated in FIG. 1 and FIG.2, the dimensions are set as follows: a width W of the silica glassmember 10 for hermetic sealing illustrated in FIG. 2: 3.5 mm, a length Lof the silica glass member 10 for hermetic sealing illustrated in FIG.2: 7 mm, a diameter d of each of lens-like convex portions 28illustrated in FIG. 2: 3 mm, and a thickness t of a portion at asubstrate joining plain surface 24 a illustrated in FIG. 1: 1 mm.

The silica glass member 10 for hermetic sealing includes a silica glasssubstrate 10A, which is homogeneously and integrally formed without aninternal boundary, and is configured to emit light in a wavelength rangeof from 250 nm to 350 nm. The silica glass substrate 10A has a firstsurface 24 on an inside opposed to the SMD LED element 12 and a secondsurface 26 on an outside corresponding to the first surface 24. Theouter peripheral portion of the first surface 24 has formed therein thesubstrate joining plain surface 24 a for joining to the container outerperiphery joining plain surface 22 a. Meanwhile, the second surface 26on the outside corresponding to the first surface 24 has formed thereinthe lens-like convex portions 28 configured to process emitted lightfrom the ultraviolet SMD LED elements 12. In the example illustrated inFIG. 1, there is illustrated an example in which two lens-like convexportions 28 are formed in a parallel state with a connecting flatportion 30 interposed therebetween, corresponding to the two ultravioletSMD LED elements 12 being placed in the hermetic sealing container 14.

With reference to the configuration described above, its action isdescribed. Under a state in which the container outer periphery joiningplain surface 22 a of the hermetic sealing container 14, in which thetwo ultraviolet SMD LED elements 12 are placed on the bottom wall 16,and the substrate joining plain surface 24 a are joined to each other,the hermetic sealing container 14 is covered with the silica glassmember 10 for hermetic sealing, to thereby bring the inside of thehermetic sealing container 14 into a hermetically sealed state. Thus,emitted light from the ultraviolet SMD LED elements 12 is processed withsatisfactory light extraction efficiency.

The shape of the silica glass substrate 10A may be as illustrated inFIG. 1 to FIG. 3, in which the entirety of the first surface 24 isformed to be a plain surface and the second surface 26 has formedtherein the lens-like convex portions 28 each having a hemisphericalshape. However, the shape of the silica glass substrate 10A is notlimited thereto, and any other shape may also be adopted as long as theshape can process emitted light from the ultraviolet SMD LED elements12.

Examples of other shapes of the silica glass substrate 10A areillustrated in FIG. 4 and FIG. 5. In the example illustrated in FIG. 4,the two lens-like convex portions 28 are each formed in a hemisphericalshape having formed therein a hollow portion 32. In the exampleillustrated in FIG. 5, as the two lens-like convex portions 28, thelens-like convex portions 28 each having a hemispherical shape areformed in the second surface 26 as in FIG. 1, while hanging enlargedportions 34 each having an ellipsoidal shape are formed in the firstsurface, corresponding to the two lens-like convex portions 28 eachhaving a hemispherical shape. Also when the hermetic sealing container14 in which the ultraviolet SMD LED elements 12 are placed is broughtinto a hermetically sealed state using the silica glass member 10 forhermetic sealing with the silica glass substrate 10A having the shape ofeach of FIG. 4 and FIG. 5, emitted light from the ultraviolet SMD LEDelements 12 can be processed with satisfactory light extractionefficiency, as with the example of FIG. 1 to FIG. 3.

One embodiment of a method of manufacturing a quartz glass member for anultraviolet LED according to the present invention is described below.In the manufacturing method of the present invention, anoxygen-deficient defect is generated by a chlorine-based gas to be usedin purification treatment intended to remove a metal impurity, but heattreatment with an oxidizing atmosphere for repairing theoxygen-deficient defect is performed to repair the oxygen-deficientdefect. Thus, there can be obtained a quartz glass member for anultraviolet LED improved in light absorption at a wavelength of about250 nm and free of absorption due to a structural defect at a wavelengthof from 200 nm to 400 nm. An atmosphere containing oxygen and/or watervapor is suitably used as the oxidizing atmosphere.

In addition, in terms of transmittance, bubbles, surface shape, and thelike, which are required characteristics for use as an optical memberfor an ultraviolet LED, characteristics equal to or higher than those ofquartz glass produced by subjecting bulk quartz glass to grindingprocessing are required, and quartz glass to be suitably used for anoptical member for an ultraviolet LED can be obtained by the followingmethod.

In a molding step, after mixing of silica powder and binder component,the raw materials subjected to kneading involving degassing treatmentmay be molded with a metal mold. In a heat treatment step, the followingsteps are performed: a degreasing step at 1,000° C. or less with anatmosphere containing oxygen; a purification step for a metal impurityat 1,200° C. or less with an atmosphere containing hydrogen chloride;and a step of repairing an oxygen-deficient defect at a wavelength ofabout 250 nm at 1,150° C. or less with an oxidizing atmosphere. Avitrification step after the heat treatment step is suitably performedat 1,700° C. or less. An Al concentration in the silica powder servingas a main raw material is suitably 70 ppm or less. It is more preferredthat heating treatment with a hydrogen atmosphere be performed after thevitrification step. With this, quartz glass to be suitably used for anoptical member for an ultraviolet LED can be obtained.

The degassing treatment of the raw material has an effect of suppressingthe generation of bubbles during the vitrification step.

Examples of the binder component include cellulose-based components(methyl cellulose, carboxymethyl cellulose, and hydroxyethyl alcohol),agar, vinyl-based components (polyvinyl alcohol and polyvinylpyrrolidone), starch-based components (dialdehyde starch, dextrin, andpolylactic acid), acrylic components (sodium polyacrylate and methylmethacrylate), and a plant viscous substance. Of those, polyvinylalcohol or methyl cellulose is suitable.

When the temperature of the degreasing step exceeds 1,000° C.,crystallization proceeds during this step to make it difficult toperform vitrification into transparent glass again through thesubsequent steps. Therefore, the degreasing step is suitably performedat 1,000° C. to 400° C., more preferably 1,000° C. to 600° C.

The purification step becomes more effective as its temperatureincreases. However, when the temperature exceeds 1,200° C., shrinkage ofa molded body proceeds to make it difficult for a gas to penetrate theinside of the molded body in the treatment with an atmosphere containingoxygen and/or water vapor in the next step, to thereby reduce the effectof repairing an oxygen-deficient defect. Therefore, the purificationstep is suitably performed at 1,200° C. to 800° C., more preferably1,200° C. to 1,000° C.

When the temperature of the step of promoting repairing of anoxygen-deficient defect exceeds 1,150° C., likewise, crystallizationbecomes liable to proceed to make it difficult to perform vitrificationinto transparent glass. Therefore, the step of promoting repairing of anoxygen-deficient defect is suitably performed at 1,150° C. to 800° C.,more preferably 1,100° C. to 950° C.

It is known that, when the silica powder serving as a main raw materialor any of various additives contains a metallic element as an impurity,crystallization is accelerated in various heat treatments, and inparticular, as a heat treatment temperature increases, the rate of thecrystallization increases. In the present invention, when Al is presentin the silica powder at a concentration of more than 70 ppm, atransparent glass body cannot be obtained, and a white and opaquecrystallized product is obtained. Therefore, the Al concentration of thesilica powder is preferably 70 ppm or less.

When the molding step is performed with a metal mold, the glass membercan be produced in a larger quantity and more inexpensively than byprior art grinding and polishing processing, and hence a greatcontribution can be made to the widespread use of ultraviolet LEDs.Injection molding, press molding, transfer molding, or the like may besuitably used as a molding method.

In addition, when the glass member is subjected to the heat treatmentwith a hydrogen atmosphere, hydrogen molecules can be incorporated intothe glass, and hence the following effect can be expected: even when astructural defect is generated in the glass by light emitted by anultraviolet LED, the structural defect is repaired.

Through the use of the method of manufacturing a quartz glass member foran ultraviolet LED of the present invention, the silica glass member forhermetic sealing of the present invention can be suitably manufactured.

EXAMPLES

Now, the present invention is more specifically described by way ofExamples. Needless to say, however, the present invention is not limitedto these Examples.

Example 1

(Formation of Plastic Matter)

79 Parts by weight of mixed powder obtained by mixing sphericalsynthetic silica powder having a diameter of 1.2 μm (product name:ADMAFINE SO-E3) and spherical synthetic silica powder having a diameterof 2 μm (product name: ADMAFINE SO-E5) at a weight ratio of 1:1, 20parts by weight of an aqueous solution of 7.8 wt % METOLOSE (productname: SM-4000), and 1 part by weight of a lubricant (product name:UNILUBE 50 MB-2) were mixed and then kneaded with a triple roll mill toform plastic matter. The term “plastic matter” as used herein refers toa kneaded product of silica glass powder, in a state of having higherviscosity than a slurry, and having hardness and plasticity comparableto those of a clay.

(Degassing Operation)

The formed plastic matter is degassed by being further kneaded underreduced pressure. Specifically, for example, kneading extrusion isperformed using a kneading extrusion molding machine manufactured byMiyazaki Iron Works Co., Ltd. under a reduced pressure of 0.1 MPa, withthe result that the generation of bubbles after sintering can be reducedto a required degree.

(Molding with Metal Mold)

The plastic matter subjected to the degassing treatment wasinjection-molded into a metal mold at an increased pressure of 120 MPato provide a molded body having a predetermined shape. Here, with regardto the metal mold, the surface roughness of a sealing portion of a plainsurface portion needs to be finished to 0.1 μm or less, preferably 0.05μm or less in terms of Ra value. Similarly, the surface roughness of alens-like projecting portion also needs to be finished to 0.1 μm orless, preferably 0.05 μm or less in terms of Ra value. Further, as amold shape, a plain surface part for sealing needs to satisfy very highflatness in order to realize hermetic sealing, but in the case of ametal mold, sufficient flatness can be realized even with generalprocessing accuracy.

(Air Drying)

The removed molded body (hereinafter green body) was air-dried in aclean atmosphere having a cleanliness level of about 10,000 at roomtemperature for about 12 hours.

(Atmosphere Heat Treatment)

The green body after the drying was put in a silica glass containerhaving a flat bottom portion, and together with the container, wassubjected to heat treatment in a horizontal tubular furnace having afurnace core tube made of silica glass under various atmospheres andtemperatures.

(Degreasing)

The temperature in the furnace was increased from room temperature at atemperature increase rate of 20° C./min to 800° C. and kept thereat. Theatmosphere at the time of the temperature increase is 100% nitrogen.After the temperature in the furnace had stabilized at 800° C., nitrogenwas stopped, and the temperature was kept for 1 hour while oxygen wasflowed at a concentration of 100%. Thus, organic matter, such asMETOLOSE, contained in the green body was completely oxidized andremoved.

(Purification)

After the completion of the degreasing treatment with an oxygenatmosphere, the oxygen was switched to 100% nitrogen, and thetemperature in the furnace was again increased at a temperature increaserate of 20° C./min to 1,200° C. and kept thereat. The nitrogen wasswitched to 100% hydrogen chloride, and purification treatment withhydrogen chloride was performed for 1 hour. The purification treatmentreduces the concentrations of metal impurities, such as an alkali metal,iron, and copper, in silica glass. Meanwhile, hydrogen chloride gasreacts with Si—OH in the silica glass to form a Si—Cl bond, and hence,when the green body after the purification treatment is sintered as itis, the following reaction occurs: 2Si.Cl→Si═Si+Cl₂. The Si═Si bond is astructural defect called an oxygen-deficient defect. The Si═Si bond hasabsorption at a wavelength of 245 nm, and at the same time, hasextremely weak resistance to ultraviolet light. Accordingly, the defectis not suited for the purpose of the present invention, and hence needsto be cured.

(Oxidation)

After the purification treatment, the hydrogen chloride serving as theatmosphere gas was switched to 100% nitrogen, and the furnacetemperature was decreased at a temperature decrease rate of 20° C./minto 1,050° C. and kept at 1,050° C. In addition, after it was confirmedthat the furnace temperature had reached 1,050° C., the nitrogen wasswitched to 100% oxygen, and the temperature was kept for 1 hour. Afterthe treatment, the oxygen was replaced with nitrogen, followed bycooling to room temperature, and the resultant was removed.

(Sintering)

The removed green bodies were arranged on a smooth carbon plate withtheir convex portions facing up, and were placed in a vacuum furnace.The inside of a vacuum chamber was evacuated to a vacuum (1×10⁻² Pa),and then the temperature was increased at a temperature increase rate of20° C./min to 1,650° C., and kept at 1,650° C. for 20 minutes while avacuum break (normal pressure 10 MPa) was performed with nitrogen. Afterthat, electricity was turned off to cool the furnace. After 10 hours,the resultant was removed. Thus, a silica glass member for LED hermeticsealing of interest was obtained.

(Evaluation)

(1) Surface Roughness Data (Surface Roughness Data on Sealing Portionand Lens Portion)

The surface roughness of a sealing portion (substrate joining plainsurface) and a convex portion were measured with a Mitutoyo surfaceroughness meter. The results are shown in Table 1. It was confirmed thatthe surface roughness of each of the portions fell within apredetermined range. In Table 1, measurement results at threemeasurement points (n) are shown.

TABLE 1 Portion Ra (μm) Measurement length Speed Sealing n = 3 0.139 2mm 0.5 mm/sec portion 0.133 0.167 Average 0.146 Max 0.167 Min 0.133Convex n = 3 0.376 0.5 mm 0.1 mm/sec portion 0.327 0.244 Average 0.316Max 0.376 Min 0.244

(2) Transmittance Data

Transmittance measurement cannot be performed for a lens shape.Therefore, a transparent flat plate measuring 20 mm×20 mm×2 mm wasproduced using exactly the same materials and manufacturing method asthose of Example 1 and subjected to general transmittance measurement(measurement apparatus: UV/VIS/NIR SPECTROMETER LAMBDA 900 manufacturedby PerkinElmer, Inc.). The results are shown in Table 2 and FIG. 6(graphical representation of an apparent transmittance and a theoreticaltransmittance). An internal transmittance for ultraviolet light having awavelength of 300 nm to 400 nm and an internal transmittance forultraviolet light having a wavelength of 245 nm or more and less than300 nm were determined from the apparent transmittance by thecalculation expression shown below. The internal transmittances areshown in Table 2. It was confirmed that each of the internaltransmittances fell within a predetermined range.

Internal Transmittance: determined from (AT/TT)×100 for an apparenttransmittance AT % at a thickness of 3 mm using a theoreticaltransmittance TT % (value obtained by subtracting reflection losses at afront surface and a back surface from 100%) of quartz glass at eachwavelength shown in Table 2.

TABLE 2 Numerical Range of Transmittance derived from Example 1Theoretical Apparent Internal Wavelength transmittance of transmittanceof transmittance of (nm) Example 1 (%) Example 1 (%) Example 1 (%) 40092.9 90.2 97.1 350 92.7 89.6 96.6 300 92.5 88.7 96.0 250 92.0 87.2 94.8245 91.9 87.1 94.7

Transmittance Measurement with Integrating Sphere: measured usingmeasurement apparatus: UV/VIS/NIR SPECTROMETER LAMBDA 900 manufacturedby PerkinElmer, Inc., integrating sphere: MODEL#150MM RSA ASSY. Theresults are shown in Table 3 and FIG. 7 together with the results of thegeneral transmittance measurement, and calculated differencestherebetween are shown in Table 3. As apparent from Table 3, it wasconfirmed that the differences each fell within a predetermined range.

TABLE 3 General Integrating sphere Difference measurement (%)measurement (%) (%) Average value for 89.56 89.89 0.33 wavelengths offrom 345 nm to 355 nm Average value for 88.73 89.07 0.34 wavelengths offrom 295 nm to 305 nm Average value for 87.21 87.63 0.41 wavelengths offrom 245 nm to 255 nm

(3) Measurement of Diameters and Numbers of Bubbles: Transmittancemeasurement cannot be performed for a lens shape. Therefore, atransparent flat plate measuring 20 mm×20 mm×2 mm was produced usingexactly the same materials and manufacturing method as those of Example1, and was further divided and polished to produce three transparentflat plates (volume: 0.1 cm³) each measuring 10 mm×10 mm×1 mm. Thediameters and numbers of bubbles were measured for those transparentflat plates with a microscope at a magnification of 100 times. Finally,the cross-sectional areas of the bubbles were converted to values per0.1 cm³ of volume. The measurement results are shown in Table 4. Nobubble having a bubble diameter of 50 μm or more was observed. As amethod of calculating an area, the maximum value of a bubble class wastaken as a diameter (for example, calculation was performed assuming 20μm to 30 μm as a diameter of 30 μm). It was confirmed that the use ofsilica glass having such cross-sectional area of bubbles enabled use asa silica glass member for hermetic sealing for an SMD package with asufficiently suppressed scattering intensity.

TABLE 4 Cross-sectional Total cross- Bubble area of bubbles sectionalarea diameter of each class of bubbles Sample No. (μm) Number (mm²)(mm²) 1 Up to 10  3 3.93E−05 9.03E−04 10 to 20 1 1.57E−04 20 to 30 03.53E−04 30 to 40 1 6.28E−04 40 to 50 0 9.82E−04 2 Up to 10  5 1.96E−047.07E−04 10 to 20 1 1.57E−04 20 to 30 1 3.53E−04 30 to 40 0 0.00E+00 40to 50 0 0.00E+00 3 Up to 10  4 1.57E−04 4.71E−04 10 to 20 2 3.14E−04 20to 30 0 0.00E+00 30 to 40 0 0.00E+00 40 to 50 0 0.00E+00

(4) OH Group Concentration: The OH group concentration of a silica glasssample measuring 20 mm×20 mm×2 mm produced using the same materials andmanufacturing method as those of Example 1 was measured with an infraredspectrophotometer, and as a result, the contained OH group concentrationwas found to be 1.3 ppm. Further, in the oxygen treatment of Example 1,the oxygen was humidified by bubbling with water, and as a result, asilica glass body having OH group concentration of 4.6 ppm was obtained.When each of those samples was irradiated with ultraviolet light havinga wavelength of 254 nm, fluorescence was not observed. Thus, the sampleswere each found to be suited as a silica glass member for hermeticsealing for an SMD package for a UV-LED.

Comparative Example 1

A planar silica glass plate material and a hemispherical lens were eachindependently produced, polished, and bonded to each other using any ofadhesives A to E described below to produce a silica glass member havinga shape similar to that of Example 1, which was subjected totransmittance measurement. The results are shown in FIG. 8. In FIG. 8,for comparison, the transmittance of the silica glass member of Example1 is also shown. As apparent from FIG. 8, all the silica glass membersjoined with the adhesives were found not to have sufficient transmissionproperties for UVB (falling within a wavelength range of from 315 nm to280 nm) and UVC (falling within a wavelength range of from 280 nm to 200nm).

The adhesives A to E are as described below.

Adhesive A: vinyl chloride resin-based adhesive AR-066 manufactured byCemedine Co., Ltd. (for bonding a vinyl chloride tube)

Adhesive B: thermosetting silicone-based adhesive KE-1886 manufacturedby Shin-Etsu Chemical Co., Ltd. (e.g., a rubber for electrical andelectronic sealing)

Adhesive C: water glass-based adhesive 37271-01 manufactured by KantoChemical Co., Inc. (for bonding ceramic or glass)

Adhesive D: synthetic rubber-based adhesive #14331 manufactured byKonishi Co., Ltd. (for bonding leather, synthetic rubber, or urethanefoam)

Adhesive E: acrylic modified adhesive AX-033 manufactured by CemedineCo., Ltd. (for bonding a metal, glass, or rubber)

Example 2

(Molding Step)

79 Parts by weight of mixed powder obtained by mixing powder having anaverage particle diameter of 1.0 μm (ADMAFINE SO-E3 manufactured byAdmatechs Company Limited) and powder having an average particlediameter of 2.0 μm (ADMAFINE SO-E5 manufactured by Admatechs CompanyLimited) at a weight ratio of 1:1, 20 parts by weight of an aqueoussolution of 7.8% methylcellulose (METOLOSE SM-4000 manufactured byShin-Etsu Chemical Co., Ltd.), and 1 part by weight of a lubricant(UNILUBE 50 MB-2 manufactured by NOF Corporation) were mixed and thenkneaded with a triple roll mill. Through the use of a vacuum extrusionmolding machine, the mixture was degassed, and subjected to kneadingextrusion under a reduced pressure of 0.1 MPa.

The mixture of the silica powder and the binder subjected to thedegassing treatment was injection-molded into a metal mold at anincreased pressure of 120 MPa to provide a molded body having apredetermined shape. Here, with regard to the metal mold, an in-planesurface roughness needs to be finished to 0.1 μm or less, preferably0.05 μm or less in terms of Ra value.

The thus produced molded body was air-dried in a clean atmosphere havinga cleanliness level of about 10,000 at room temperature for about 12hours.

(Heat Treatment Step)

The molded body after the drying was put in a quartz glass containerhaving a flat bottom portion, and together with the container, wassubjected to heat treatment in a horizontal tubular furnace having afurnace core tube made of quartz glass under various atmospheres andtemperatures. In the heat treatment step, the following steps (a) to (c)were performed.

(a): (Degreasing Step)

The temperature in the furnace was increased from room temperature at atemperature increase rate of 20° C./min to 800° C. and kept thereat. Theatmosphere at the time of the temperature increase is 100% nitrogen.After the temperature in the furnace had stabilized at 800° C., nitrogenwas stopped, and the temperature was kept for 1 hour while oxygen wasflowed at a concentration of 100%. Thus, organic matter, such asMETOLOSE, contained in the molded body was completely oxidized andremoved.

(b): (Purification Step)

After the completion of the degreasing treatment with an oxygenatmosphere, the oxygen was switched to 100% nitrogen, and thetemperature in the furnace was again increased at a temperature increaserate of 20° C./min to 1,200° C. and kept thereat. The nitrogen wasswitched to 100% hydrogen chloride, and purification treatment withhydrogen chloride was performed for 1 hour. The purification treatmentreduces the concentrations of metal impurities, such as an alkali metal,copper, and iron, in quartz glass. Meanwhile, hydrogen chloride reactswith Si—OH in the quartz glass to form a Si—Cl bond, and hence, when themolded body after the purification treatment is vitrified as it is, thefollowing reaction occurs: 2Si·Cl→Si═Si+Cl₂. The Si═Si bond is astructural defect called an oxygen-deficient defect. The Si═Si bond hasabsorption at a wavelength of about 250 nm, and at the same time, hasextremely weak resistance to ultraviolet light. Accordingly, the defectis not suited for the purpose of the present invention, and hence needsto be cured.

(c): (Step of Promoting Repairing of Oxygen-Deficient Defect)

After the purification treatment, the hydrogen chloride serving as theatmosphere gas was switched to 100% nitrogen, and the temperature wasdecreased at a temperature decrease rate of 20° C./min to 1,050° C. andkept thereat. The nitrogen was switched to oxygen 100%, and treatmentfor repairing an oxygen-deficient defect in quartz glass with oxygen wasperformed for 1 hour. After the treatment, the oxygen was switched to100% nitrogen, followed by cooling to room temperature, and theresultant was removed.

(Vitrification Step)

The removed molded bodies were arranged on a smooth carbon plate, andplaced in a vacuum furnace. The inside of a vacuum chamber was evacuatedto a degree of vacuum of 1×10⁻² Pa, and then the temperature wasincreased at a temperature increase rate of 20° C./min to 1,650° C.After having reached 1,650° C., the temperature was kept for 10 minuteswhile a vacuum break was performed with nitrogen to increase thepressure to 0.1 MPa. After that, electricity was turned off to cool thefurnace. After 10 hours, the resultant was removed. Thus, a quartz glassmember for an ultraviolet LED of interest was obtained.

(Evaluation)

Physical property values were evaluated in accordance with the followingmeasurement methods.

(1) Al Concentration

The obtained quartz glass member was decomposed with hydrofluoric acid,and subjected to measurement by ICP emission spectrometry.

(2) External Appearance

The obtained quartz glass member was visually observed. A case oftransparent quartz glass was evaluated as “Satisfactory”, a case ofbeing opaque due to crystallization (devitrification) was evaluated as“Crystallization”, and a case of containing visually recognizablebubbles was evaluated as “Bubbles”.

(3) Absorption at Wavelength of 250 nm

A flat plate measuring 20 mm×20 mm×2 mm was produced, and subjected tomeasurement with a UV-VIS spectrophotometer in the wavelength range offrom 200 nm to 400 nm to confirm the presence or absence of absorptionat a wavelength of 250 nm. A case in which absorption at a wavelength of250 nm was absent was evaluated as “Absent”, a case in which theabsorption was present was evaluated as “Present”, and a case in whichcrystallization made measurement impossible was evaluated as“Unmeasurable”.

Various conditions and measurement results are collectively shown inTable 5. The transmittance measurement results of the quartz glassmember for an ultraviolet LED obtained in Example 2 at wavelengths offrom 200 nm to 400 nm are shown in FIG. 9.

Example 3

A quartz glass member for an ultraviolet LED was obtained in the samemanner as in Example 2 except that the treatment for repairing anoxygen-deficient defect was performed at a temperature of 1,050° C., andunder an atmosphere containing water vapor produced by a methodinvolving bubbling pure water kept at 30° C. with oxygen serving as acarrier.

Example 4

The quartz glass member for an ultraviolet LED obtained in Example 2 wassubjected to hydrogen treatment in a hydrogen atmosphere at 400° C. and0.8 MP (heating treatment with a hydrogen atmosphere) to introducehydrogen molecules into the glass. Thus, a quartz glass member for anultraviolet LED was obtained.

Example 5

A quartz glass member for an ultraviolet LED was obtained by performingthe same treatments as in Example 2 except that mixed powder obtained bymixing powder having an average particle diameter of 0.25 μm (ADMAFINESO-E1 manufactured by Admatechs Company Limited), powder having anaverage particle diameter of 1.0 μm (ADMAFINE SO-E3 manufactured byAdmatechs Company Limited), and powder having an average particlediameter of 2.0 μm (ADMAFINE SO-E5 manufactured by Admatechs CompanyLimited) at a weight ratio of 1:1:2 was used as a raw material.

Comparative Example 2

A quartz glass member was obtained in the same manner as in Example 2except that the step of promoting repairing of an oxygen-deficientdefect was not performed. The transmittance measurement results of thequartz glass member obtained in Comparative Example 2 at wavelengths offrom 200 nm to 400 nm are shown in FIG. 10.

Comparative Example 3

Treatments were performed in the same manner as in Example 2 except thatthe degreasing temperature of the degreasing step in the heat treatmentstep was set to 1,100° C. The state after the heat treatment step wasnot particularly different from that of the sample of Example 2, andhence the sample of Comparative Example 3 was subjected tovitrification, but became opaque due to crystallization.

Comparative Example 4

Treatments were performed in the same manner as in Example 2 except thatthe purification temperature of the purification step in the heattreatment step was set to 1,350° C. Although the volume of the sinteredbody after the heat treatment step was slightly shrunk, the sinteredbody was subjected to vitrification as it was. As a result, a largenumber of extremely fine bubbles were mixed therein.

Comparative Example 5

Treatments were performed in the same manner as in Example 2 except thatthe oxygen defect repairing temperature of the step of promotingrepairing of an oxygen-deficient defect in the heat treatment step wasset to 1,200° C. The state after the heat treatment was not particularlydifferent from that of the sample of Example 2, and hence the sample ofComparative Example 5 was subjected to vitrification, but became opaquedue to crystallization.

Comparative Example 6

The glass member obtained in Comparative Example 2 was kept in an oxygenatmosphere at 1,100° C. for 10 hours. The transmittance of the resultantsample was measured. As a result, it was found that, although absorptionat a wavelength of 250 nm was slightly improved, the transmittance inthe entire region of from 200 nm to 400 nm was reduced due to theinfluence of contamination caused by the heat treatment.

TABLE 5 Example Example Example Example Comparative ComparativeComparative Comparative Comparative 2 3 4 5 Example 2 Example 3 Example4 Example 5 Example 6 Degreasing Temperature   800   800   800   800  800 1,100   800   800   800 (° C.) Atmosphere Oxygen Oxygen OxygenOxygen Oxygen Oxygen Oxygen Oxygen Oxygen Purification Temperature 1,2001,200 1,200 1,200 1,200 1,200 1,350 1,200 1,200 (° C.) AtmosphereHydrogen Hydrogen Hydrogen Hydrogen Hydrogen Hydrogen Hydrogen HydrogenHydrogen chloride chloride chloride chloride chloride chloride chloridechloride chloride Defect Temperature 1,050 1,050 1,050 1,050 Absent1,050 1,050 1,200 Absent repair (° C.) Atmosphere Oxygen Water OxygenOxygen Oxygen Oxygen Oxygen vapor + oxygen Vitrification Temperature1,650 1,650 1,650 1,650 1,650 1,650 1,650 1,650 1,650 (° C.) AtmosphereVacuum Vacuum Vacuum Vacuum Vacuum Vacuum Vacuum Vacuum Vacuum Alconcentration of   50   50   50   70   50   50   50   50   50 silicapowder (ppm) Oxygen treatment Absent Absent Absent Absent Absent AbsentAbsent Absent Present after vitrification Hydrogen treatment AbsentAbsent Present Absent Absent Absent Absent Absent Absent Externalappearance Satis- Satis- Satis- Satis- Satis- Crystal- Bubbles Crystal-Satis- factory factory factory factory factory lization lization factoryAbsorption at wavelength Absent Absent Absent Absent Present Unmea-Present Unmea- Present of 250 nm surable surable

REFERENCE SIGNS LIST

10: silica glass member for hermetic sealing, 10A: silica glasssubstrate, 14: hermetic sealing container, 16: bottom wall, 18: sidewall, 20: opening, 22: upper end outer peripheral portion, 22 a:container outer periphery joining plain surface, 24: first surface, 24a: substrate joining plain surface, 26: second surface, 28: lens-likeconvex portion, 30: connecting flat portion, 32: hollow portion, 34:hanging enlarged portion.

1. A silica glass member for hermetic sealing of an ultraviolet SMD LEDelement that is configured to emit light in a wavelength range of from250 nm to 350 nm and is placed in a hermetic sealing container having acontainer outer periphery joining plain surface formed in an outerperipheral portion thereof, the silica glass member for hermetic sealingcomprising: a silica glass substrate, which is homogeneously andintegrally formed without an internal boundary, wherein the silica glasssubstrate has: a first surface on an inside opposed to the SMD LEDelement; and a second surface on an outside corresponding to the firstsurface, wherein an outer peripheral portion of the first surface hasformed therein a substrate joining plain surface for joining to thecontainer outer periphery joining plain surface, and the second surfaceon the outside corresponding to the first surface has formed therein alens convex portion configured to process emitted light from theultraviolet SMD LED element.
 2. A silica glass member for hermeticsealing according to claim 1, wherein a plurality of the lens convexportions are formed on the second surface.
 3. A silica glass member forhermetic sealing according to claim 1, wherein the substrate joiningplain surface formed in the first surface has a surface accuracy equalto 1 μm or less and a surface roughness of 0.05 μm to 0.3 μm in terms ofRa value, and the lens convex portion in the second surface has asurface roughness of 0.05 μm to 0.5 μm in terms of Ra value.
 4. A silicaglass member for hermetic sealing according to claim 1, wherein thesilica glass member for hermetic sealing has an internal transmittanceat a thickness of 3 mm of 95% to 99% for ultraviolet light having awavelength of 300 nm to 400 nm and an internal transmittance at athickness of 3 mm of 92% to 99% for ultraviolet light having awavelength of 245 nm or more and less than 300 nm.
 5. A silica glassmember for hermetic sealing according to claim 1, wherein respectivedifferences between internal transmittances of the silica glass memberfor hermetic sealing at a thickness of 3 mm for ultraviolet light havingwavelengths of 350 nm, 300 nm, and 250 nm measured using an integratingsphere and internal transmittances thereof at a thickness of 3 mm forultraviolet light having wavelengths of 350 nm, 300 nm, and 250 nm ingeneral measurement are each within 0.5%.
 6. A silica glass member forhermetic sealing according to claim 1, wherein bubbles contained in thesilica glass member for hermetic sealing each has a diameter equal to 50μm or less, and the bubbles contained have a total cross-sectional areaequal to 1×10⁻³ mm² or less per 0.1 cm³ of a volume of the silica glassmember for hermetic sealing.
 7. A silica glass member for hermeticsealing according to claim 1, wherein the silica glass member forhermetic sealing contains OH groups at a concentration of 0.1 ppm to 20ppm.
 8. A method for manufacturing a quartz glass member for anultraviolet LED, the method comprising: a molding step of mixing silicapowder and a binder component to form a resultant mixture, followed bymolding the resultant mixture to obtain a molded body having apredetermined shape; a heat treatment step of subjecting the molded bodyto heating treatment with various gases; and a vitrification step ofvitrifying the molded body subjected to heat treatment into transparentglass after the heat treatment step, the heat treatment step comprising:a degreasing step for organic matter at 1,000° C. or less with anatmosphere containing oxygen; a purification step for a metal impurityat 1,200° C. or less with an atmosphere containing hydrogen chlorideafter the degreasing step; and a step of promoting repairing of anoxygen-deficient defect at a wavelength of about 250 nm at 1,150° C. orless with an oxidizing atmosphere after the purification step.
 9. Amethod according to claim 8, wherein the molding step comprises amolding step with a metal mold.
 10. A method according to claim 8,wherein the oxidizing atmosphere comprises an atmosphere containing oneor more of oxygen and water vapor.
 11. A method according to claim 8,wherein the vitrification step is performed at 1,700° C. or less.
 12. Amethod according to claim 8, wherein the silica powder contains at leastone kind of spherical silica, and the silica powder has an Alconcentration of 70 ppm or less.
 13. A method according to claim 8,further comprising performing heating treatment with a hydrogenatmosphere after the vitrification step.
 14. A method according to claim8, wherein the ultraviolet LED is configured to emit ultraviolet lighthaving a wavelength of from 200 nm to 400 nm.